This invention relates to a europium activated strontium tetraborate phorphor. It also relates to a process for producing the phosphor by a new chemical precipitation technique which results in the phosphor having essentially complete homogeneity of constituents including essentially complete incorporation of the europium activator and particle size control.
Ultraviolet emitting fluorescent lamp phosphors have been on the market for a number of years. However, phosphors emitting long wavelength, narrow band U.V. are essentially limited to europium activated strontium haloborates. Such phosphors are disclosed in U.S. Pat. Nos. 3,431,215 and 3,431,216. These phosphors are prepared by a multi-step process involving complex chemical precipitation of europium doped SrB.sub.6 O.sub.10.5H.sub.2 O. This material is filtered, dried, and then combined with a strontium halide. The mixture is then air fired, ground, and blended with additional strontium halide and finally refired under H.sub.2 /N.sub.2 and ground once more to achieve the desired particle size. The process is labor intensive and produces a product with a poorly developed particle habit with concomittant reduction of its theoretical emission efficiency.
German Patent Application Disclosure DE No. 3400385 A1 entitled "Low Pressure Mercury Vapor Discharge Lamp" describes europium activated strontium tetraborates. A europium activated strontium tetraborate containing fluroine is disclosed which is described as being equivalent to the material disclosed in U.S. Pat. No. 3,431,215. There is no indication in the German application of how this phosphor is produced. German Patent Application Disclosure No. 2,652,480 discloses europium activated strontium tetraborates which have either barium or magnesium.